STUDY ON THE ANALYSIS OF TAXONOMIC DISTANCE AMONG

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Prokaryotes were phylogenetically classified by 16SrRNA sequences and genetic distance among independent species were quantitatively measured simply by comparing their 16SrRNA differences. However, it become clear that some established species shares same 16SrRNA sequences.In this case, we need to use other method to differentiate closely related species. Quantitative DNA/DNA hybridization method is a officially accepted method to define a bacterial species. However, this method is difficult to perform and DNA used for this method is often cotaminated with polysaccharide, which interfers quantitative analysis of DNA/DNA hybrid. We established several parameters to evaluate DNA purity and a rapid measuring method of guanine plus cytosine contents of DNA to define DNA/DNA hybridization experiments. RNA and polysaccharide contamination was successfully predicted by measuring absorbance of 235/260 nm and Anthrone quantitation method of sugars. Guanine plus cytosine content of DNA was instantly measured by Light cycler with SYBR Green 1 fluorescence. This information is very useful to define quantitative DNA/DNA hybridization at optimal temperature. Trials to differentiate strains within a species were successfully introduced by many scientists. We used Ceul restriction enzyme to evaluate distances among strains. This method has a advantage because bands generated by the Ceul digestion indicate numbers of copies of ribosomal RNA operon. From fragment analysis of generated size offered useful information to analyze gene recombination history.